The invention relates generally to a seating system which permits pressure compensation, and more particularly to a seat cushion and positioning assembly which can be tailored to fit the needs of individuals who use wheelchairs.
The art of seating has grown to a science involving considerations of physiology, material science, and ergonomics. The present invention relates to a seating assembly designed specifically for individuals confined to a wheelchair with the goal of providing long-term comfort and improved health. Further, the insert of the present invention can be filled to an appropriate pressure to meet individual needs and preferences of a user. While the present invention encompasses multiple aspects, overall goals include maintenance of good health, and comfort of the user. The present invention provides a unique approach and features for posture correction and further services the goal of minimizing the risk of decubitus ulcers.
A first aspect of the invention provides a foam base cushion which is firm but compressible such as provided by an open or closed cell polyurethane foam. The base has a rear depression having a rounded shape which is situated to fit under the user""s bottom including ischial tuberosities (i.e. the seat bones) as well as the trochanters of the person seated on the cushion (i.e., xe2x80x9cthe userxe2x80x9d).
In a preferred embodiment, the depression has a smoothly spherical or concave surface with the lowest point under and between the ischial tuberosities and which rises gradually upwardly from a gently rounded bottom and blends with the surface of the cushion. Thus, the depression is generally xe2x80x9cbowl-shapedxe2x80x9d. The depression may be hemispherical or may be elongated in the direction of the width of the chair so as to form an ovoid or elliptical shape. The rear depression supports an insert which acts to position the user by supporting the trochanters. The seat bones are ultimately supported by an inflatable top compression insert which has a perimeter shape so as to fit within the rear depression and form a substantially flat appearance in the rear of the cushion. As the user""s trochanters are positioned on the air insert, a novel method of positioning is provided in which the skeletal structure of the user is positioned rather than using the prior art reliance on soft tissue. Thus, the present invention provides the advantage of avoiding reliance on soft tissue as a seating support since, in many people who use wheelchairs, the quality and consistency of the muscular tissue is poor.
In a further aspect of the invention, the insert includes a plurality of inflatable pleated air cells which project upwardly from a flat (i.e. planar) bottom. The cells are in fluid communication with each other. The insert is constructed of a flexible material and will correspond generally to or take on the shape of the recess into which it is put. It is important however, that the recess rises upwardly on the sides to provide a proper support for the invalid user.
Moreover, the insert is connected by means of a quick connect fitting to a hand held pump which can be inflated with a single hand, such as a squeezable balloon pump. Thus, the insert can be inflated with a single hand so as to allow the user or a technician to use his or her other hand to check the fill level of the insert. Moreover, the fitting can be a one-way valve as to permit fill while the individual is seated on the cushion. This allows instant input from the user of the cushion during set-up. The insert includes means to affix the insert to the base cushion such as for example adhesive or hook and loop fasteners.
Optionally, the present invention can be used with a bowl shaped intermediate insert also including a seating well which can be positioned between the air filled pressure insert and the base cushion. The use of the intermediate insert enables a positioning which can be further tailored for a particular user. For example, when a user has a scoliosis causing a lateral asymmetry in the pelvic region, the depression can be angled to accommodate or to correct for the problem. This angle can be infinitely adjusted including additional adjustment over time to suit the changing needs of an individual user.
In addition, transverse lateral stabilizers are provided on the bottom side of the cushion and can comprise elongated wedge members having a generally triangular cross-section which support the outer side edges of the cushion from the bottom. The lateral stabilizers or wedges are generally constructed of a material which is stiffer, or more rigid than the base cushion such as closed cell polyurethane foam. Otherwise, the bottom side of the cushion is relatively flat so as to correspond to the shape of a base support of the wheelchair or a rigidizer member which provides a planar surface for sling seats.
The top surface of the base cushion optionally includes contouring such as elevated sides, a front pommel, and ridge so as to define leg wells and rear rims to provide further support to the soft tissue of the user""s bottom. These contours may provide additional positioning support for the user.